Power Quality AU Q& A DOC

Title	Power Quality AU Q& A
Author	Ezhilmaran M
Pages	20
File Size	2.6 MB
File Type	DOC
Total Downloads	444
Total Views	498

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MAY/JUN-'09/EE1004-Answer Key PARTA- (10 x 2=20 marks) 1. How a capacitor switching leads to an over voltage?(2) One-line diagram of a capacitor-switching operation corresponding to the waveform 2. What is the basic difference between CBEMA and ITI curves? The CBEMA curve has become a standard design target for sensitive equipment to be applied on the power system. ITI curve applies to common 120-V computer equipment. 3. 3.Mention any two solutions against voltage sags. ?(2) 1. Equipment manufacturers should have voltage sag ride-through capability curves (similar to the ones shown previously) available to their customers so that an initial evaluation of the equipment can be performed. Customers should begin to demand that these types of curves be made available so that they can properly evaluate equipment. 2. The company procuring new equipment should establish a procedure that rates the importance of the equipment. If the equipment is critical in nature, the company must make sure that adequate. 3. Equipment should at least be able to ride through voltage sags with a minimum voltage of 70 percent (ITI curve). The relative probability of experiencing voltage sag to 70 percent or less of nominal is much less than experiencing sag to 90 percent or less of nominal. A more ideal ride-through capability for short-duration voltage sags would be 50 percent, as specified by the semiconductor industry in Standard SEMI F-47.17 4. How to estimate the voltage sag performance? ?(2) 1. Determine the number and characteristics of voltage sags that result from transmission system faults. 2. Determine the number and characteristics of voltage sags that result from distribution system faults (for facilities that are supplied from distribution systems). 3. Determine the equipment sensitivity to voltage sags. This will determine the actual performance of the production process based on voltage sag performance calculated in steps 1 and 2. 4. Evaluate the economics of different solutions that could improve the performance, either on the supply system (fewer voltage sags) or within the customer facility (better immunity). 5. How is overvoltage different from swell? ?(2) An overvoltage is an increase in the rms ac voltage greater than 110 percent at the power...